Caliper Pistons: Ok to Spin?

Originally Posted by plowsie

YC is this a good guide to go by? They say WD40, surely thats asking for trouble...

http://www.motorcyclenews.com/MCN/ad...ce/?&R=EPI-668

As you say seems a bit dodgy. Brake fluid is vegetable based and the rubber used in the seals formulated on that basis. Mineral based fuilds, like WD40 and engine oil will cause brake seals designed for vegetable fluid to expand. So I would stick with brake cleaner or brake fluid to clean pistons, unless they are removed from the caliper in which case the seals wont come in contact with the WD40

Would brake cleaner on the pistons end up damaging the seals over time?

Originally Posted by yorkie_chris

Better to use a bit of thin card with some solvol on it, or the serrated edge of a cable tie to clean around them.

God damn it you're a genius!

Now then, what about step 1 from the MCN guide...

1. Gently squeeze the brake pads against the pistons by gripping them with water-pump pliers against the caliper then remove the retaining pin(s) that are holding the pads in place.

Am I not going to bend/twist/knacker something doing that? I've been taking the caliper off and then removing the pads.

[yorkie_chris]

Quite possibly. At the least you will take the paint off your caliper.

You shouldn't need to press the pads back hardly at all to remove them.

To press the pistons back in, you should be able to use your hands if the caliper is healthy, with waterpump pliers you risk getting the piston trying to go into the bore slightly sideways if there is any resistance to movement. (i.e any corrosion behind the seals, which there will be!)

[yorkie_chris]

Originally Posted by skyline

Would brake cleaner on the pistons end up damaging the seals over time?

IMO it evaporates so quick it is unlikely it has time to penetrate into the seals and do damage.

WD40 on the other hand is pretty non-volatile, AFAIK it is based on paraffin.

Nice one, thanks Mr Chris!

[yorkie_chris]

With the 2-pots on the SV you should be able to get plenty purchase by hand, or a straight-push at them with a G clamp.

You should need practically no force to push them back. If you need to beast them then they need rebuilding.

Originally Posted by yorkie_chris

with waterpump pliers you risk getting the piston trying to go into the bore slightly sideways if there is any resistance to movement.

Well that's what I thought! Break out the bunting.